Make the python test scripts work on python3

The python scripts invoked by 'make check' didn't work on python3
before.  That was a problem on systems where 'python' is python3.

Fixes bug 11608; bugfix on 0.2.5.2-alpha.

1 files changed, 25 insertions, 6 deletions

diff --git a/src/test/slownacl_curve25519.py b/src/test/slownacl_curve25519.py
index 25244fb122..4dabab61b6 100644
--- a/src/test/slownacl_curve25519.py
+++ b/src/test/slownacl_curve25519.py
@@ -8,12 +8,14 @@
 
 __all__ = ['smult_curve25519_base', 'smult_curve25519']
 
+import sys
+
 P = 2 ** 255 - 19
 A = 486662
 
 def expmod(b, e, m):
   if e == 0: return 1
-  t = expmod(b, e / 2, m) ** 2 % m
+  t = expmod(b, e // 2, m) ** 2 % m
   if e & 1: t = (t * b) % m
   return t
 
@@ -23,12 +25,14 @@ def inv(x):
 # Addition and doubling formulas taken from Appendix D of "Curve25519:
 # new Diffie-Hellman speed records".
 
-def add((xn,zn), (xm,zm), (xd,zd)):
+def add(n,m,d):
+  (xn,zn), (xm,zm), (xd,zd) = n, m, d
   x = 4 * (xm * xn - zm * zn) ** 2 * zd
   z = 4 * (xm * zn - zm * xn) ** 2 * xd
   return (x % P, z % P)
 
-def double((xn,zn)):
+def double(n):
+  (xn,zn) = n
   x = (xn ** 2 - zn ** 2) ** 2
   z = 4 * xn * zn * (xn ** 2 + A * xn * zn + zn ** 2)
   return (x % P, z % P)
@@ -40,19 +44,34 @@ def curve25519(n, base):
   # (m+1)th multiple of base.
   def f(m):
     if m == 1: return (one, two)
-    (pm, pm1) = f(m / 2)
+    (pm, pm1) = f(m // 2)
     if (m & 1):
       return (add(pm, pm1, one), double(pm1))
     return (double(pm), add(pm, pm1, one))
   ((x,z), _) = f(n)
   return (x * inv(z)) % P
 
+if sys.version < '3':
+    def b2i(c):
+        return ord(c)
+    def i2b(i):
+        return chr(i)
+    def ba2bs(ba):
+        return "".join(ba)
+else:
+    def b2i(c):
+        return c
+    def i2b(i):
+        return i
+    def ba2bs(ba):
+        return bytes(ba)
+
 def unpack(s):
   if len(s) != 32: raise ValueError('Invalid Curve25519 argument')
-  return sum(ord(s[i]) << (8 * i) for i in range(32))
+  return sum(b2i(s[i]) << (8 * i) for i in range(32))
 
 def pack(n):
-  return ''.join([chr((n >> (8 * i)) & 255) for i in range(32)])
+  return ba2bs([i2b((n >> (8 * i)) & 255) for i in range(32)])
 
 def clamp(n):
   n &= ~7